In recent years, images and displays have become three-dimensional and 3D information acquisition techniques have been actively developed. There are many expected applications of a 3D range image sensor capable of acquiring 3D spatial information in real time. For example, the 3D range image sensor is applied to a gesture recognition system, a computer vision system, or the like. Non-Patent Document 1 discloses a 3D TOF range image sensor that acquires range image information by irradiation of an object with light from a light source. The use of the sensor enables a small low-cost system as compared to the use of a 3D stereo range image sensor, a 3D laser scan range image sensor, or the like.
In addition, a motion recognition technique by which position change information, shape change information, and the like of an object are detected and motion information is recorded digitally has been widely used in areas such as sports medicine, movies, and computer animation. Patent Document 1 discloses an information processor including a user interface for detecting user's complicated motion easily.
Patent Document 2 discloses a system that calculates 3D range image information from a plurality of two-dimensional (2D) images acquired by imaging with a plurality of cameras and recognizes the motion of an object. Further, Patent Document 3 discloses a human body motion recognition sensor that recognizes the motion of a human body by detecting an infrared ray emitted from the human body.